The present invention is concerned with the handling of can end closures or lids, for example, as a preliminary to delivery of the lids into an end seaming operation for can bodies. Typically, the lids are supplied in sticks consisting of a stack of such lids which are placed in a downstacker mechanism and individually fed from the bottom onto a starwheel for transfer onto a rotary table where sealant is applied to the lid as a preliminary to delivery of each lid to the end seaming operation. For instance, U.S. Pat. No. 4,262,629 to McConnellogue et al, assigned to the assignee of this invention, sets forth and describes an end lining mechanism for the application of sealant to the can lids and which includes a single downstacker mechanism for successively advancing can lids into the end lining table.
A continuing problem encountered in the handling of can lids is the high rate of speed required for their delivery in order to coordinate with the rest of the can-forming operation; and, when feed screws are employed to advance each lid into registry with a starwheel, has in the past required a full revolution of the feed screws before the lid would clear the downstacker and be free to advance with the rotating starwheel. In order to employ two or more downstackers along the path of travel of the starwheel not only requires close coordination in the timing of delivery of lids from each downstacker into alternate pockets of the starwheel but modification of the feed screws and more positive advancement of the lid into each pocket in order to minimize the possibility of jamming. Furthermore, it is desirable to reduce the speed of rotation of the feed screws without reducing the rate of delivery of lids from each stack onto the starwheel; and to be able to deliver lids from one stack in the event that the supply of lids becomes depleted in the other stack so that the entire downstacker operation need not be suspended.
It has been proposed to provide end feeding devices wherein the can lids can be successively removed from dual stacks and fed into a transfer mechanism or table. Typically, however, each stack must be rotated into alignment with the transfer mechanism and reference is made to U.S. Pat. No. 3,253,722 to DeGear for that approach to end closure feeding apparatus. Other patents of interest in this field are U.S. Pat. Nos. 1,126,194 to C. W. Graham, 1,161,931 to J. W. Dixon, 1,415,937 to W. Lippitz, 2,184,029 to S. Wicklund, 2,743,001 to R. E. J. Nordquist and 3,158,289 to L. C. Van Brunt. However, the systems disclosed in these patents are not capable of alternately feeding lids from a pair of stationary downstacks in the path of travel of the starwheel, nor are they capable of continuously supplying can lids from one downstacker in the event that the supply of lids should become depleted in the other downstacker.